(b 1) Field of the Invention:
The present invention relates to a honeycomb structural body-extruding die apparatus which can produce honeycomb structures of a good quality.
(2) Related Art Statement:
Heretofore, honeycomb structures have been produced by a honeycomb structural body-extruding die apparatus shown in FIG. 3, which comprises an extruding die 13 with holes 11 for feeding a material to be extrusion-shaped (hereinafter referred to as "extruding material-feeding holes"), which holes are formed on an extruding material inlet side, as well as shaping channels 12 communicated to one another in a lattice fashion on an extruding material outlet side, and a die mask 14 provided around the outer periphery of an end face of the extruding die 13 on the extruding material outlet side.
In the above-mentioned conventional apparatus, since an outer peripheral wall is formed by squeezing the extruding material having passed through the outer peripheral portion of the extruding die at a tapered inner peripheral wall of the die mask 14, a speed of discharging the extruding material through the shaping channels of the die is greater at the outer peripheral portion than at the central portion. Therefore, there is a drawback in that cell deformation is likely to appear in an obtained honeycomb structural body near the outer peripheral wall thereof as seen at a portion "A" in FIG. 4. In order to eliminate such a drawback, Japanese patent publication No. 58-23,207 (U.S. Pat. No. 4,368,025) discloses a honeycomb structural body-extruding die apparatus in which a plurality of grooves are opened at a small interval along an inner peripheral edge portion of a die mask in contact with an end face of a die for feeding an extruding material forcedly fed into shaping channels at the peripheral portion of the die to the inside of the die mask.
However, since no attention is paid to a difference in a discharging speed of the fed extruding material between the central portion and the outer peripheral portion in the above die apparatus, either, deformation of cells cannot be completely removed. Further, in the case that a plurality of the openings are provided along the inner periphery of the die mask, the dimension of such openings of the die mask needs to be slightly varied depending upon a shrinkage factor of the extruding material. In addition, to determine where a plurality of such openings are to be provided in what direction for the extrusion of honeycomb structures is extremely troublesome.